This invention relates to halogen-containing resins having as the result of incorporation therein of a new stabilizer composition comprising at least two different compounds containing tin and sulfur greatly improved resistance to deterioration in color, processability and mechanical properties on exposure to elevated temperatures.
There is an enormous number of disclosures of tin compounds that have been used to stabilize halogen containing resins such as polyvinyl chloride, vinyl chloride copolymers, and other vinyl halide polymers. To illustrate the unmanageably large bulk of this literature, it might be noted that a 1959 review booklet by H. Verity Smith titled "The development of the Organotin Stabilizer" (published by Tin Research Institute, Greenford, England) listed over 100 patent disclosures of tin containing stabilizers for PVC, and more recently C. Stapfer in U.S. Pat. No. 3,830,751 of Aug. 20, 1974 listed over 500 individual tin containing compounds and L. Weisfeld in U.S. Pat. No. 3,887,519 of June 3, 1975 listed over 200 compounds that are all methyltin derivatives, i.e. compounds with at least one methyl group directly linked to tin, including for example dimethyltin sulfide. Overwhelmingly the tin containing stabilizers referred to in this literature are tin compounds having at least one hydrocarbon group linked to 4-valent tin through carbon, for example methyl, n-butyl, and n-octyl. The remarkably small number of disclosures of tin containing stabilizers other than 4-valent tin derivatives with at least one hydrocarbon group linked to tin are represented by J. Fincke U.S. Pat. No. 2,479,918 of Aug. 23, 1949, tetra(2-thienyltin); S. Caldwell U.S. Pat. No. 2,629,700 of Feb. 24, 1953, carboxylate salts of 2-valent (stannous) tin; W. Leistner U.S. Pat. No. 2,726,227 of Dec. 6, 1955, certain tetrahydrocarbon mercaptides of tin having only hydrocarbon groups linked to tin through sulfur; W. Considine in U.S. Pat. No. 3,412,120 of Nov. 19, 1968 disclosed cyanoalkylenetin sulfides having linked to tin one or two cyanoalkylene groups having two or more carbon atoms in the alkylene group made from tetrakis (cyanoalkylene) tin by halogenation or redistribution to the required cyanoalkylenetin halide; Considine also showed in U.S. Pat. No. 3,454,609 of July 8, 1969 that when cyanoalkylenetin compounds were hydrolyzed, polymeric propionatotin compounds were obtained. Akzo N.V. in Netherlands Specification No. 74-12230 of Mar. 16, 1976 disclosed functional substituted organotin trihalides prepared from stannous halide, hydrogen halide, and carbonyl group activated olefins of the type R.sub.1 R.sub.2 C.dbd.CR.sub.3 R.sub.4 where at least one R group is an activating group with a carbonyl radical adjoining the double bond and the other R groups are hydrogen or alkyl groups, and converted to mercaptoester type stabilizers; Akzo N.V. Netherlands Specification No. 75-03116 of Sept. 17, 1976 functional substituted organotin dihalides prepared from tin metal, hydrogen halide, and carbonyl group activated olefins of the type R.sub.1 R.sub.2 C.dbd.CR.sub.3 R.sub.4 where at least one R group is an oxygen containing group with a carbonyl group adjoining the double bond and the other R groups are hydrogen or alkyl groups, and converted to stabilizers by reaction with alkylthiocarboxylic acid esters, alkylthiols, monocarboxylic acids, or partial esters of dicarboxylic acids.
Pertinent to the evaluation of the present invention among the large number of known hydrocarbontin sulfur compounds are particularly the use of hydrocarbontin sulfides by E. Weinberg in U.S. Pat. Nos. 2,746,946 of May 22, 1956 and 2,789,103 of Apr. 16, 1957; and by M. Crauland in U.S. Pat. No. 3,108,126 of Oct. 22, 1963; alkylstannonic acids and alkylthiostannonic acids (i.e. monohydrocarbontin sulfides) by H. Frey in U.S. Pat. No. 3,021,302 of Feb. 13, 1962; cyclic dihydrocarbyltin salts of mercapto carboxylic acids by G. Mack in U.S. Pat. No. 3,027,350 of Mar. 27, 1962; thiobis(dihydrocarbontin) salts of carboxylic acids and dicarboxylic acid monoesters by A. Schroeder in U.S. Pat. No. 3,476,404 of Nov. 4, 1969; an organotin stabilizing agent obtained by reacting a compound of the formula R--Sn--(X).sub.3 wherein R is a hydrocarbon and X halogen, with a mixture of an alkali metal sulfide and (a) aliphatic alkali metal mercaptide or (b) an alkali metal salt of a saturated or unsaturated mono or polycarboxylic acid, by C. Dorfelt in U.S. Pat. No. 3,442,852 of May 6, 1969; organotin mercaptoacid ester sulfides having the formula: ##STR1## in which n is an integer from one to two, m is the number of COOR.sub.1 groups, and is an integer from one to four, x is an integer from zero to one, R is a hydrocarbon radical having from about one to about eighteen carbon atoms, and preferably from four to eight carbon atoms, R.sub.1 is an organic group derived from a monohydric or polyhydric alcohol of the formula R(OH).sub.n4, where n.sub.4 is an integer from one to about four, but is preferably one or two; R.sub.2 is R or SZ (COOR.sub.1).sub.m ; Z is a bivalent alkylene radical carrying the S group in a position alpha or beta to a COOR.sub.1 group, and can contain additional free carboxylic acid, carboxylic ester, or carboxylic acid salt groups, and mercapto groups; and the Z radical has from one to about five carbon atoms, by O. Kauder in U.S. Pat. No. 3,565,930 of Feb. 23, 1971; reaction products of ogano-tin mercaptoacid derivatives having the formula ##STR2## as well as R.sub.n Sn(SR'COOR").sub.4n and (RSn(SR'COOR").sub.2).sub.2 X wherein R is an alkyl radical having up to 12 carbons, R" is an alyl radical, R' is an alkylene group of at least 2 methylene groups, X is oxygen or sulfur, n is 1 to 3 and y designates the degree of polymerization, with an organotin oxide, a monohydrocarbyltin oxide, or a hydrocarbylstannoic acid or ester thereof, by L. Weisfeld in U.S. Pat. No. 3,576,785 of Apr. 27, 1971; and alkyltin polysulfide thioesters having the formula (R.sub.x Sn).sub.n (--SR'COOR").sub.(4-x)n-2m (--S.sub.y).sub.m where the tin is tetravalent, R is alkyl of 1 to 8 carbon atoms or benzyl, R' is alkylene of 1 to 4 carbon atoms, R" is alkyl of 1 to 18 carbon atoms or alkenyl of 2 to 18 carbon atoms, cycloalkyl having 5 to 6 carbon atoms in the ring, or benzyl, x is 1 or 2, y is 2 to 4, n is 1 to 10 and m is 1/2n to n, by T. Kugele in U.S. Pat. No. 3,869,487 of Mar. 4, 1975.
There have also been disclosures of the combined use of different kinds of stabilizers containing tin and sulfur. Thus C. Stapfer in U.S. Pat. No. 3,503,616 of Mar. 24, 1970 disclosed the use in PVC of a monoalkyltin sulfide and a dialkyltin sulfide. J. Gottlieb in U.S. Pat. No. 3,424,717 of Jan. 28, 1969 disclosed the use in PVC of a first stabilizer having the formula (RSnX.sub.1,5).sub.n wherein R is alkyl having 1 to 20 carbon atoms, aryl, alkaryl, aralkyl, and cycloalkyl, and X is oxygen, sulfur, or a mixture of these, and n is 2-1000; a second stabilizer which is a 2,6-di substituted phenol with the substituents being branched alkyl groups having less than 10 carbon atoms; and a third stabilizer R'.sub.a Sn(SR").sub.4-a where R' is hydrocarbon, R" a residue of a carboxylic acid, a carboxylic ester, or a hydrocarbon, and a is 1 to 3. O. Kauder in U.S. Pat. No. 3,632,538 of Jan. 4, 1972 disclosed a stabilizer composition having a high concentration of tin, within the range from about 20 to about 35% Sn, comprising an organotin alpha- or beta-mercapto carboxylic ester and an organotin sulfide. The organic groups linked to tin in the organotin sulfide are hydrocarbon or heterocyclic groups; the organic groups linked to tin through carbon in the organotin mercapto acid esters are hydrocarbon groups having from about one to about eight carbon atoms. For best results at least one of the compounds of the combination should have only one hydrocarbon group per tin atom linked to tin through carbon. Similar compositions of organotin ester and sulfide are also disclosed by P. Hoye in U.S. Pat. No. 3,609,120 of Sept. 28, 1971. L. Weisfeld in U.S. Pat. No. 3,640,950 of Feb. 8, 1972 disclosed combinations of diorganotin compounds, particularly dialkyltin mercaptides, mercaptoesters, and mercapto acid salts, with small amounts of monohydrocarbyltin salts to eliminate a yellowish cast in halogenated vinyl resins stabilized with diorganotin salts alone. W. Mayo in U.S. Pat. No. 3,769,263 of Oct. 30, 1973 disclosed vinyl resin stabilized with a first stabilizer (RSnX.sub.1,5 ).sub.n and a second stabilizer R'.sub.2 Sn(SR").sub.2 wherein R, R', R", and n are defined as in Gottlieb U.S. Pat. No. 3,424,717 already cited. L. Brecker in U.S. Pat. No. 3,787,357 of Jan. 22, 1974 disclosed homogeneous liquid stabilizers containing both a monoalkyltin mercaptocarboxylic acid ester and a dialkyltin mercaptocarboxylic acid ester together with a barium containing liquid in which barium carbonate is dispersed in an organic salt such as a barium alkylphenolate or alkylaromatic sulfonate acting as a liquefying agent for barium carbonate.
Throughout the cited disclosures of stabilizers containing more than one kind of organotin-sulfur compound, the organic groups linked to tin through carbon in these compounds are hydrocarbon groups.